Einstein Theory Proved

Gravity Probe B has provided the first experimental evidence of the geodetic effect, one of two key propositions of Einstein’s general relativity theory.

In the most commonly used analogy for general relativity, space is compared to a rubber mat stretched flat. The surface of the mat bends if a heavy object is placed on it. In a similar way, the Earth bends what Einstein called “space-time.”

The NASA probe contains four ultra-precise gyroscopes to measure that curvature. The orbit of the satellite is actually a very slow fall to Earth. Because that fall is over curved space-time, the axes of the gyroscopes move differently to how they would were the surface of space-time flat. Like a ship going prow-first into a whirlpool, the axes are tipped on the approach to earth.

Over the next eight months, the probe will return data to test the second key prediction of general relativity: frame-dragging. Does the Earth’s spinning drag space-time, making it spin like the whirlpool in the above analogy?

“Gravity Prove B is the relativity gyroscope experiment developed by NASA and Stanford University to test two unverified predictions of Albert Einstein’s general theory of relativity.” NASA provides elegant animations illustrating the curvature of space-time.

Albert Einstein was born in Germany on March 14, 1879. He received the Nobel Prize in Physics in 1921. “At the start of his scientific work, Einstein realized the inadequacies of Newtonian mechanics and his special theory of relativity stemmed from an attempt to reconcile the laws of mechanics with the laws of the electromagnetic field.”

The “special theory of relativity” shows that time and length are not absolute, but their values vary; it also produced the world’s most famous equation, E=MC2, describing the equivalence of mass and energy. The “general theory of relativity” demonstrated mathematically the curvature of space and time.

The short answer to the question of what is the General Theory of Relativity is that “according to Einstein the presence of a gravitational field alters the rules of geometry in space-time. The effect is to make it seem as if space-time is ‘curved’.”

As with much of science, general relativity is counter-intuitive. Time can travel at different speeds for different people; two people can measure the same object with perfect accuracy and produce different results; mass and energy are different expressions of the same force. This section of the NASA Web site tries to shed some light on these difficulties.